feat: support resolving deps for a non-host interpreter version

With this PR we prepare the dependency resolution machinery to
support other than host python versions. This may make it possible
to generate select statements based on the version but we target
this usecase as it requires little code to be changed and once
wired to the starlark code could be of use. Creating this PR
for discussion so that we can decide on a suitable interface.

Author: aignas

python/pip_install/tools/wheel_installer/wheel.py

@@ -84,10 +84,20 @@ def _as_int(value: Optional[Union[OS, Arch]]) -> int:
     return int(value.value)
 
 
+class MinorVersion(int):
+    @classmethod
+    def host(cls) -> "MinorVersion":
+        version = platform.python_version()
+        _, _, tail = version.partition(".")
+        minor, _, _ = tail.partition(".")
+        return cls(minor)
+
+
 @dataclass(frozen=True)
 class Platform:
     os: OS
     arch: Optional[Arch] = None
+    minor_version: MinorVersion = MinorVersion.host()
 
     @classmethod
     def all(cls, want_os: Optional[OS] = None) -> List["Platform"]:
@@ -235,11 +245,12 @@ def env_markers(self, extra: str) -> Dict[str, str]:
             "platform_system": self.platform_system,
             "platform_release": "",  # unset
             "platform_version": "",  # unset
+            "python_version": f"3.{self.minor_version}",
+            # FIXME @aignas 2024-01-14: is putting zero last a good idea?
+            "implementation_version": f"3.{self.minor_version}.0",
+            "python_full_version": f"3.{self.minor_version}.0",
             # we assume that the following are the same as the interpreter used to setup the deps:
-            # "implementation_version": "X.Y.Z",
             # "implementation_name": "cpython"
-            # "python_version": "X.Y",
-            # "python_full_version": "X.Y.Z",
             # "platform_python_implementation: "CPython",
         }
 
@@ -400,8 +411,9 @@ def _add_req(self, req: Requirement, extras: Set[str]) -> None:
             ]
         )
         match_arch = "platform_machine" in marker_str
+        match_version = "version" in marker_str
 
-        if not (match_os or match_arch):
+        if not (match_os or match_arch or match_version):
             if any(req.marker.evaluate({"extra": extra}) for extra in extras):
                 self._add(req.name, None)
             return
@@ -414,8 +426,10 @@ def _add_req(self, req: Requirement, extras: Set[str]) -> None:
 
             if match_arch:
                 self._add(req.name, plat)
-            else:
+            elif match_os:
                 self._add(req.name, Platform(plat.os))
+            elif match_version:
+                self._add(req.name, None)
 
     def build(self) -> FrozenDeps:
         return FrozenDeps(

python/pip_install/tools/wheel_installer/wheel_test.py

@@ -152,6 +152,43 @@ def test_self_dependencies_can_come_in_any_order(self):
         self.assertEqual(["bar", "baz", "zdep"], got.deps)
         self.assertEqual({}, got.deps_select)
 
+    def test_can_get_deps_based_on_specific_python_version(self):
+        requires_dist = [
+            "bar",
+            "baz; python_version < '3.8'",
+            "posix_dep; os_name=='posix' and python_version >= '3.8'",
+        ]
+
+        py38_deps = wheel.Deps(
+            "foo",
+            requires_dist=requires_dist,
+            platforms=[
+                wheel.Platform(
+                    os=wheel.OS.linux, arch=wheel.Arch.x86_64, minor_version=8
+                ),
+            ],
+        ).build()
+        py37_deps = wheel.Deps(
+            "foo",
+            requires_dist=requires_dist,
+            platforms=[
+                wheel.Platform(
+                    os=wheel.OS.linux, arch=wheel.Arch.x86_64, minor_version=7
+                ),
+            ],
+        ).build()
+
+        self.assertEqual(["bar", "baz"], py37_deps.deps)
+        self.assertEqual({}, py37_deps.deps_select)
+        self.assertEqual(["bar"], py38_deps.deps)
+        self.assertEqual({"@platforms//os:linux": ["posix_dep"]}, py38_deps.deps_select)
+
+
+class MinorVersionTest(unittest.TestCase):
+    def test_host(self):
+        host = wheel.MinorVersion.host()
+        self.assertIsNotNone(host)
+
 
 class PlatformTest(unittest.TestCase):
     def test_can_get_host(self):